Apparatus for controlling the taper of wood boards formed by a chipless cutting operation

ABSTRACT

Sheets of wood are cut from a timber piece along a guide and against a  cung blade. A transverse taper of the wood piece is measured as the wood piece is conveyed. In accordance with changes in the measured transverse taper, the guide or the blade is pivoted about an axis extending perpendicular to the blade edge as the wood piece is being conveyed. Also, the longitudinal taper of the wood piece can be measured as the wood piece is conveyed. In accordance with the changes in the measured longitudinal taper, the distance between the blade edge and the wood guide is varied as the wood piece is conveyed.

BACKGROUND OF THE INVENTION

The invention relates to a device for cutting sheets of wood off squaretimber without forming chips, said device comprising a machine frame anda feeding device, which conveys the square timber in the longitudinaldirection against a cutter blade, slanted at an angle to said squaretimber, with a pressure bar, which is located at a distance from thecutter blade and is attached to a wood guide surface.

It is well-known to use, instead of the sawing method, the cuttingmethod (DE-A-37 02 909), which does not form chips and thus functionsvirtually without a loss, in order to produce sheets of wood from asquare timber. It is also well-known to adjust in the case of a deviceof the aforementioned class (DE-A-40 26 346) the thickness of the sheetsof wood produced or the thin boards by changing the distance between thecutter blade and the adjacent pressure bar by means of a settingmechanism. In the prior art device this distance is set as a function ofthe result of the measurement of the square timber prior to each cuttingoperation. With this known device the thickness of each individual sheetof wood that is produced can be influenced; however, the taper cannot beinfluenced.

In everyday operations, however, there is a need to influence preciselythe taper of the sheets of wood, which are produced, in the transversedirection, in order to compensate for a variation in thickness betweenboth longitudinal edges of the sheet of wood.

Such a difference in the thickness of the sheet of wood in thetransverse direction also occurs when the cutter blade is arrangedexactly parallel to the wood guide surface. Since the sheet of wood tobe cut during the cutting operation is compressed between the cutterblade and the pressure bar, which is rigidly attached to the wood guidesurface, the compressibility of the wood, which is usually cut in themoist state, affects the resulting thickness of the sheet of wood.

The compressibility depends, however, on the growth ring arrangement inthe cross section of the wood, and in particular, the angle at which thegrowth rings run with respect to the surface of the sheet of wood. Owingto the approximately circular pattern of the growth rings in the crosssection of the trunk, this angle of the growth rings relative to thesurface of the sheet of wood varies over the width of said sheet ofwood. The result is that in most cases the thickness of the twolongitudinal edges of the sheet of wood that is produced variesimmediately after the cutting operation, a state that is called "taperin the transverse direction".

In the known device (DE-A-40 26 346) the setting of the cutter blade iscontrolled in such a manner as a function of the measured thickness ofthe square timber that the waste sheet, remaining after the last cuttingoperation exhibits, the same thickness as the other sheets of wood, thusmaintaining a specified tolerance. If, however, the square timber is cutconically as a consequence of the varying compressibility in thetransverse direction, these conical variations can add up in the manysuccessive cutting operations in such a manner that the resulting wastesheet exhibits such a severe taper in the transverse direction that itis not suitable for further processing, even though its thickness isstill within the permissible tolerance.

In another known device (DE-A-39 26 396) the pressure bar opposite thecutter blade is pivot-mounted on the wood guide surface. However, thepivoting motion takes place around a swivel axis, which extends inessence parallel to the cutter blade. Such a pivotability is notprovided and also not suitable for compensating a taper of the squaretimber, especially since there is no relative adjustment between thewood guide surface and the cutter blade. Thus, in this device only thepressure conditions over the entire length of the cutter blade changeuniformly. However, the thickness and/or the taper of the sheets of woodproduced is not affected.

Therefore, the object of the invention is to design a device of theaforementioned class in such a manner that an error in taper resultingduring the cutting operation can be automatically compensated.

SUMMARY OF THE INVENTION

This problem is solved according to the invention by arranging at adistance from each other two measurement devices for the thickness ofthe square timber in the transverse direction of the square timber andin that there is a relative pivoting motion between the cutter blade andthe wood guide surface, which is connected to the pressure bar, around aswivel axis, which extends in essence at right angles to the cutterblade, as a function of the measurement result, determined by themeasurement devices, by means of a swivel control.

A taper of the square timber in the transverse direction is determinedby measuring the square timber at two measurement points, which arespaced laterally apart. The cutting operation is changed in such amanner by means of the subsequent relative pivoting motion of the cutterblade and the wood guide surface, carrying the pressure bar, that thetaper of the square timber is compensated to such an extent that theremaining waste sheet does not exhibit any taper beyond the permissibleamount in the transverse direction. The thickness of the waste sheet cancorrespond either to the thickness of the other sheets or be countedlarger, thus resulting in a subsequent machining operation during whichthe waste sheet obtains the desired thickness.

The relative pivoting motion can be carried out in such a manner thatthe wood guide surface, guiding the square timber, with the pressurebar, which is attached to said wood guide surface, is rigidly mounted tothe frame and that the cutter blade is attached to a cutter holder,pivot-mounted on the machine frame.

Instead of the above arrangement, the cutter blade can also be mountedrigidly on the frame and the wood guide surface, connected to thepressure bar, can be pivot-mounted on the machine frame.

In another embodiment of the inventive idea it is provided that, inaddition to this relative pivoting motion between the cutter blade andthe wood guide surface or independently thereof, a taper in thelongitudinal direction of the square timber is also compensated. Inaddition, it is provided according to the invention that the distancebetween the cutter blade and the wood guide surface, connected to thepressure bar, can be adjusted during the passage of the square timber bymeans of a setting mechanism as a function of at least two measurementsof the thickness of the square timber, said measurements being done at acertain longitudinal distance.

With these measurements a taper of the square timber in the longitudinaldirection is determined. The distance between the cutter blade and thewood guide surface is changed in such a manner during the travel of asquare timber that this lengthwise taper is compensated. The object ofthis measure is also that the remaining waste sheet does not exhibit anyinadmissible high taper.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in detail with reference to the embodimentsshown in the drawings.

FIG. 1 is a simplified side view of a device for cutting sheets of woodoff a square timber without forming chips.

FIG. 2 is an enlarged top view of a detail in the direction of the arrowII in FIG. 1.

FIG. 3 is a view in the direction of arrow III in FIG. 2.

FIG. 4 is a sectional view along the line IV--IV of FIG. 2.

FIG. 5 is a sectional view along the line V--V of FIG. 2.

FIG. 6 is a side view corresponding to FIG. 3 of a modified embodiment;and

FIG. 7 is a sectional view along the line VII--VII of FIG. 6.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The device depicted in FIG. 1 exhibits a feed-conveying mechanism 1, forexample a roller bed, on which a square timber 2 is fed in. Twomeasurement devices 3, 4, located at a distance from each other in thetransverse direction of the square timber 2, for example laser-thicknessmeasurement devices, detect the thickness of the square timber 2 at twopoints, which lie, as indicated in FIG. 2, side-by-side at a certaindistance (as seen in the transverse direction of the square timber 2).

In a cutting station 5 the square timber 2 is pressed by a feedingdevice 6, which exhibits in the illustrated embodiment a driven,vertically adjustable feed belt 7, against a wood guide surface 8, whichis designed as a guiding table and to whose edge is rigidly attached apressure bar 9, which slopes at an acute angle relative to thelongitudinal direction of the wood and the conveying direction of thewood.

At a distance from the pressure bar 9 or the wood guide surface 8 and inessence parallel thereto there is a cutter blade 10, against which thesquare timber 2 is pressed by means of the feed device 6. The cutterblade 10 cuts off the underside of the square timber 2 a sheet of wood11, which is removed diagonally downwardly, as shown in the schematic inFIG. 1.

After leaving the cutting station 5, the remaining square timber 2' iscarried away again to the feed-conveying device 1 and subjected again toa cutting operation. This procedure is repeated until only a waste sheetremains of the square timber 2 or 2'.

In the embodiment illustrated in detail in FIGS. 2 to 5, the wood guidesurface 8, guiding the square timber 2, and the pressure bar 9,connected to said wood guide surface, are mounted rigidly to the frame(FIG. 4). The cutter blade 10 is designed as a cutter 12, which isattached to the top side of a cutter holder 13. The cutter holder 13 ispivot-mounted on the machine frame 14, where its horizontal swivel axis15 extends in the top view (FIG. 2) at right angles to the cutter blade10. The swivel axis 15 is formed by means of a shaft 16, which isattached to a box-shaped cutter holder 13 and whose two shaft ends aremounted in a swivel bearing 17 of the machine frame 14.

As evident from FIG. 3, the cutter holder 13 is braced at a distancefrom the swivel axis 15 against a vertically adjustable abutment 18. Bymeans of this pressure 19 the cutter holder 13 is pressed without playagainst the abutment 18.

FIG. 5 shows that the abutment 18 exhibits a vertically adjustablecarrier 20, whose bottom inclined surface 21 rests against ahorizontally moveable wedge 22. The wedge 22 can be adjustedhorizontally by way of a threaded spindle 24, connected to an adjustingmotor 23, in order to be able to adjust the height of the abutment 18.

The schematic of FIG. 2 shows that the measurement results, delivered bythe measurement devices 3, 4, are fed to an evaluation circuit 25. Therethe taper of the square timber 2 in the transverse direction isdetermined as the difference in the thickness at the measurement points3, 4. The evaluation circuit 25 sends a regulate command to theadjusting motor 23, which swivels the cutter blade 10 relative to thepressure bar 9, mounted rigidly on the frame, around the swivel axis 15,in order to compensate the measured taper at least so far that theremaining waste sheet does not exhibit any inadmissible large taper inthe transverse direction.

At variance with the embodiment described and illustrated in FIGS. 1-5,the cutter holder 13 can also be swivelled around another swivel axis,provided it forms only an angle with the cutter blade 10 that is clearlynot 0°. For example, the cutter holder 13 can be swivelled around aswivel axis, extending in the conveying direction and the longitudinaldirection of the square timber 2. Important is only that during theswivelling motion the relative angular position between the cutter blade10 and the wood guide surface 8 or the pressure bar 9 changes.

Therefore, at variance with the embodiment described above it can alsobe provided that the cutter blade 10 is attached rigidly to the frameand the wood guide surface 8 performs the controlled swivelling motion.

This construction principle is realized in the embodiment according toFIGS. 6 and 7. There the wood guide surface 8 is attached with thepressure bar 9 to a pressure bar slide 26, which can be adjustedvertically in a slide guide holder 27 and thus can be moved at rightangles to the cutter blade. For this purpose the pressure bar slide 26is braced against the machine frame 14 by way of two lifting elements28, 29, which can be adjusted separately and in essence perpendicularlyto the plane of the wood. The two lifting elements 28, 29 are spacedapart in the longitudinal direction of the pressure bar 9 and areformed, for example, by a threaded spindle drive.

The slide guide holder 27 is pivot-mounted by way of a bearing shaft 30on a bearing block 31, connected to the machine frame 14. The swivelaxis 32, formed by the shaft 30, runs at right angles to the pressurebar 9 or the cutter blade 10 and parallel and at a distance from thewood guide surface 8.

If the two lifting elements 28 and 29 are actuated separately, the woodguide surface 8 is swivelled with the pressure bar 9, attached to saidwood guide surface, in the manner described above relative to the cutterblade 10, in order to compensate a taper of the square timber 2 in thetransverse direction, said taper having been determined by themeasurement devices 3, 4. As indicated in FIG. 6, the evaluation circuit25' controls the two lifting elements 28, 29 as a function of themeasurement result of the measurement devices 3, 4.

In addition to the described procedure or irrespective thereof, at leasttwo thickness measurements of the square timber can be conducted bymeans of the measurement devices 3, 4 or with only one of these twomeasurement devices 3, 4 at a certain longitudinal distance. To thisend, the measurement devices 3, 4 or one of these two measurementdevices 3, 4 are actuated once at the start of the square timber 2 andanother time at the end of the square timber 2. The measurement valuesobtained thus give information about the taper of the square timber 2 inthe longitudinal direction, i.e. the difference in the thickness at thebeginning and the end of the square timber 2.

The measurement result obtained thus is processed in such a manner inthe evaluation circuit 25' that the two lifting elements 28, 29 areactuated in such a manner during the travel of the square timber 2 thatthe distance between the cutter blade 10 and the wood guide surface 8changes continuously during passage. Thus the determined taper of thesquare timber 2 in the longitudinal direction is compensated.

If the fed-in square timber 2 exhibits both a taper in the transversedirection and in the longitudinal direction, a state that is determinedby the measurement devices 3, 4 in at least two measurement operationsevery time the square timber 2 travels through, the lifting elements 28,29 are actuated in such a manner by means of the evaluation circuit 25'that both a swivel adjustment and also a height adjustment of the woodsurface guide 8 occurs, said height adjustment occuring continuouslyduring passage.

At variance with the embodiment shown in FIGS. 6 and 7, the adjustmentmotion controlled by the evaluator 25' can also be carried out at thecutter blade 10, which can be adjusted at right angles for this purposeand may or may not be additionally pivot-mounted on the machine frame14. It is also possible to separate the swivel adjustment to compensatea taper in the transverse direction and the continuous transverseadjustment during passage of the square timber in such a manner thateither the cutter blade 10 or the wood surface guide 8 carries out onlythe swivel adjustment and the other part carries out only the heightadjustment.

We claim:
 1. Apparatus for the chipless cutting of wood sheets from apiece of square timber having a longitudinal length and a transversewidth, the apparatus comprising:a wood guide, including a pressure bar,for supporting a piece of square timber for movement, the wood guideengaging a supported side of the timber piece; a feeding device forconveying the timber piece along the wood guide in a path of travel; acutter blade having a cutting edge for cutting a wood sheet from thesupported side of the timber piece, the cutting edge extendingtransversely of the path of travel and being slanted at an oblique anglewith respect to the path of travel as viewed in a directionperpendicular to the supported side of the timber piece; a measuringmechanism arranged to measure a transverse taper of the timber piece bymeasuring the thickness of the timber piece at least at two transverselyspaced locations thereon during conveying of the timber piece; and anadjusting mechanism operably connected to the measuring mechanism forproducing a relative pivoting movement between the blade and the woodguide about a pivot axis extending substantially perpendicular to thecutting edge as viewed in a direction perpendicular to the supportedside, in accordance with variations in the measured transverse taper ofthe timber piece.
 2. Apparatus according to claim 1, wherein the woodguide is stationary, and the cutter blade is mounted for pivotaladjustment about the pivot axis, the adjusting mechanism being connectedto the cuter blade.
 3. Apparatus according to claim 1 further includinga frame, the wood guide and its pressure bar being rigidly connected tothe frame, a blade holder supporting the cutter blade being pivotablymounted to the frame for pivoting about the pivot axis.
 4. Apparatusaccording to claim 3, wherein the pivot axis extends parallel to a planeof the wood guide and at a distance therefrom.
 5. Apparatus according toclaim 1, wherein the cutter blade is stationary, and the wood guide ismounted for pivotal adjustment about the pivot axis, the adjustingmechanism being connected to the wood guide.
 6. Apparatus according toclaim 5 further including a frame, the wood guide being mounted to theframe for pivoting about the pivot axis, a blade holder for supportingthe cutter blade being rigidly mounted to the frame.
 7. Apparatusaccording to claim 6 including first and second lifting elementsconnected between the frame and the wood guide on opposite sides of thepivot axis for pivoting the wood guide.
 8. Apparatus for the chiplesscutting of wood sheets from a piece of square timber, comprising:a woodguide, including a pressure bar, for supporting a piece of square timberfor movement, the wood guide engaging a supported side of the timberpiece; a feeding device for conveying the timber piece along the woodguide in a path of travel; a cutter blade having a cutting edge forcutting a wood sheet from the supported side of the timber piece, thecutting edge extending transversely of the path of travel and beingslanted at an oblique angle with respect to the path of travel as viewedin a direction perpendicular to the supported side of the timber, thedepth of cut being determined by a spacing between the cutting edge andthe pressure bar; a measuring mechanism arranged to measure alongitudinal taper of the timber piece by measuring the thickness of thetimber piece at least at two longitudinally spaced locations thereonduring conveying of the timber piece; and an adjusting mechanismoperably connected to the measuring mechanism for changing the spacingbetween the cutting edge and pressure bar to vary the cutting depth, inaccordance with variations in the measured longitudinal taper of thetimber piece.
 9. Apparatus according to claim 8, wherein the wood guideand pressure bar are stationary, and the cutter blade is adjustable forvarying the distance between the cutter blade and the pressure bar. 10.Apparatus according to claim 8, wherein the cutter blade is stationary,and the wood guide and pressure bar are adjustable for varying thedistance between the cutter blade and the pressure bar.
 11. Apparatusaccording to claim 10 further including a frame having a holder, thewood guide and pressure bar being slidably mounted in the holder formovement in a direction substantially perpendicular to the cuttingblade.
 12. Apparatus according to claim 11, wherein the holder ispivotably mounted to the holder by a pivot axis extending substantiallyperpendicularly to the pressure bar as viewed in a directionperpendicular to the supported side of the timber piece, the pivot axisbeing parallel to a plane of the wood guide and spaced therefrom. 13.Apparatus according to claim 8 further including a frame, a pair oflifting elements mounted thereon and connected to the wood guide, thelifting elements being spaced apart in a direction parallel to thepressure bar and being simultaneously actuable to vary the distancebetween the pressure bar and cutting edge.